John Creasey is notable as the most prolific writer of mystery stories in the history of the genre. Changing from pen name to pen name and from sleuth to sleuth, Creasey mass-produced as many as two novels a week. At his death, he was credited with more than 550 crime novels, which had sold sixty million copies in twenty-six languages. Despite his great commercial success, Creasey was not highly ranked by critics, who pointed out that no matter how clever his plot outlines might be, his characters too often were pasteboard creations rather than psychologically interesting human beings, his situations geared to fast action rather than to the development of atmosphere that characterizes the best mystery novels. Sensitive to such criticisms, in some of his novels Creasey took time for fuller development of character; the Gideon series, written under the pseudonym J. J. Marric, ranks with the best of the genre.